Events at Physics
Events on Thursday, January 27th, 2011
- R. G. Herb Condensed Matter Seminar
- Shock waves in cold Fermi atoms
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Alexander Abanov, Stony Brook University
- Abstract: I will discuss a recent experiment performed by James Joseph and John Thomas in Duke University. They experimentally produced a collision between two ultra-cold atomic clouds made out of a unitary Fermi gas. During the collision a very sharp and stable density peak at the center of the trap was formed and subsequently evolved into a box-like shape. We demonstrate that we can model the nonlinear dynamics of this collision using a dimensionally reduced quasi-1D form of hydrodynamic equations of motion. The quasi-1D nonlinear hydrodynamics shows near perfect agreement with the experiment and we see a clear evidence of shock wave formation which is a hallmark of nonlinear physics.
- Host: Andrey Chubukov
- Astronomy Colloquium
- "Toward the Formation of Realistic Disk Galaxies".
- Time: 3:30 pm
- Place: 4421 Sterling Hall
- Speaker: Alyson Brooks, CALTECH
- Abstract: Much progress has been made in recent years in forming realistic disk galaxies in fully cosmological simulations. I will highlight the necessity of both 1) a physically motivated prescription for star formation and feedback and 2) very high numerical resolution to achieve a successful model for the formation of disk galaxies<br>
(including bulgeless dwarf disk galaxies). The resulting simulated galaxies simultaneously match observed disk scaling relations (stellar mass -- metallicity, size -- luminosity, size -- velocity, and velocity -- luminosity) for the first time. Realistic simulated galaxies are the necessary starting point for interpreting observations in light of galaxy formation theory. Hence, I will conclude by highlighting the science enabled by these state-of-the-art simulations.
- Host: Astronomy Department
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- New CMB Polarization Results from QUIET at 43-GHz
- Time: 4:00 pm
- Place: 4274 Chamberlin Hall
- Speaker: Immanuel Buder, University of Chicago
- Abstract: Inflationary cosmology postulates that the Universe underwent a period of accelerated expansion in the first 10^-30 s after the Big Bang. Inflationary models are attractive because they solve outstanding problems in cosmology: the origin of structure, the absence of monopoles, and the horizon and flatness problems. Although inflation is consistent with existing data, the fundamental physics responsible for it is unknown. Cosmic Microwave Background (CMB) measurements promise to verify one of the predictions of inflation: odd-parity polarization modes (B modes).
CMB B modes have not yet been detected. The Q/U Imaging ExperimenT (QUIET) recently reported a measurement of the CMB polarization at 43-GHz (Q band). This is one of the best limits to date on inflationary B modes. Moreover the unique QUIET design leads to the lowest levels of systematic contamination in the inflationary signal reported by any CMB polarization experiment.
I will describe the QUIET instrument, how it mitigates systematic contamination, and results from the first season of Q-band observation. I will also report the status of analysis of the second-season 95-GHz (W-band) data.
- Host: Peter Timbie